Ever wondered what goes on in those increadibly high frequencies that might almost be called 'nanowave' instead of 'microwave'? Well other than a bit of use for looking at the earth from satellites (a.k.a. earth observation) the main uses tend to be military. This is partly because it becomes quite difficult (and thus expensive) to generate any kind of power at these frequencies but also because even if you do, it doesn't tend to go very far because of the poor propagation characteristics. At these frequencies, signals do not penetrate very far inside solid objects such that even the thinnest membrane will stop them dead in their tracks. Even the thin blue line of atmosphere that surrounds our fragile planet is enough to nobble extra high frequencies.

But those clever military people realised that this ability of signals to not penetrate anything very deeply might have an application other than for radio communication, navigation or any of the other uses you normally associate with the spectrum. They realised that a microwave oven at a frequency of, say, 95 GHz, would only cook the very outside of anything that was put in it (at a depth of no more than a half a milimetre) and leave the insides untouched. So you could use it to char the skin of a red pepper (or capsicum as they are known in lesser countries) whilst leaving the flesh crispy and fresh. Or you could char a peach, leaving the juicy bit inside uncooked. Or you could fire a beam at a human and make them feel as if they were on fire without actually burning them. No, seriously, not only could you do this, but this is exactly what a new line of devices being used by the military (and some other governmental bodies) are actually doing.

Known as the 'Active Denial System' (or ADS for short), these devices were initially designed to use for dispersing unwanted crowds gathering at military establishments, enclaves, camps or hide-outs. By blasting protestors, marauders and other such types with several hundred watts of high frequency 95 GHz microwaves in a tightly focussed beam, you can make them feel as if they are on-fire by heating up the nerve endings near the surface of the skin without heating the skin itself. This makes for a pretty good deterent and they soon move away, out of the beam.

Prisons soon realised the potential of the ADS to 'gently direct' prisoners away from certain areas too. Los Angeles County prison has installed one of these devices and according to the prison chief officer, "we likes 'em California char grilled", though it is unclear whether he was referring to his prisoners or to his burgers.

Sadly, attempts to use the device to produce instant suntans failed, partly due to the excrutiating pain involved in standing in front of the beam but also because it's completely the wrong type of radiation! Silliness aside, if such a device could be reduced in size to become handheld, it might be possible to generate enough oomph to produce a 'heat ray' beam to temporarily disable miscreants in your immediate vicinity. Now we have moved from HG Wells' martian heat rays to Gene Roddenberry's phaser guns. What with Star Trek communication devices having been introduced in the 1990s, and Star Trek style tri-corder being oh-so similar to iPhones, the time is nigh for someone to develop a real-life warp engine to propel humanity into the future. By the way, whilst you're there, could you check whether our Oidar is working and send us a message backwards through time to let us know. Ta muchly.